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PubMed1976

Dietary protein life-span, and physiological variables in female mice.

The 50% mortality of female C57BL/6J mice fed ad libitum a diet which contained 26% or 4% casein, was 23.5 and 28 mo., respectively. Significantly lower rectal temperatures and higher oxygen consumptions were observed in the animals offered the 4% compared to the 26% casein diet. Changes in body temperature and oxygen consumption could not account for the total increase in life-span brought about by feeding a low protein diet.

Animals↗
PubMed1988

Physiological variables affecting intraocular pressure in a population study.

Intraocular pressure (IOP) and several other parameters were measured on 560 subjects as part of a vision and health screening program. The sample included a large proportion of American Indians with diabetes (15.2%) and obesity. Multiple regression analysis showed that the percentage of ideal body weight index and average blood pressure both had independent effects on IOP, whereas age, blood sugar, sex, degree of Indian blood, and diabetes did not, although the latter three variables narrowly missed having a statistically significant effect in at least one eye. The analysis of variance showed that diabetes was associated with elevated IOP. This association was independent of random blood sugar, blood pressure, obesity index, and age.

Adolescent↗
PubMed2005

Effects of playing a computer game using a bright display on presleep physiological variables, sleep latency, slow wave sleep and REM sleep.

Epidemiological studies have shown that playing a computer game at night delays bedtime and shortens sleeping hours, but the effects on sleep architecture and quality have remained unclear. In the present study, the effects of playing a computer game and using a bright display on nocturnal sleep were examined in a laboratory. Seven male adults (24.7+/-5.6 years old) played exciting computer games with a bright display (game-BD) and a dark display (game-DD) and performed simple tasks with low mental load as a control condition in front of a BD (control-BD) and DD (control-DD) between 23:00 and 1:45 hours in randomized order and then went to bed at 2:00 hours and slept until 8:00 hours. Rectal temperature, electroencephalogram (EEG), heart rate and subjective sleepiness were recorded before sleep and a polysomnogram was recorded during sleep. Heart rate was significantly higher after playing games than after the control conditions, and it was also significantly higher after using the BD than after using the DD. Subjective sleepiness and relative theta power of EEG were significantly lower after playing games than after the control conditions. Sleep latency was significantly longer after playing games than after the control conditions. REM sleep was significantly shorter after the playing games than after the control conditions. No significant effects of either computer games or BD were found on slow-wave sleep. These results suggest that playing an exciting computer game affects sleep latency and REM sleep but that a bright display does not affect sleep variables.

Adult↗
PubMed1996

Head-to-cervix force: an important physiological variable in labour. 1. The temporal relation between head-to-cervix force and intrauterine pressure during labour.

OBJECTIVE: To investigate the relation between the rise in intrauterine pressure and rise in fetal head to cervix force in normal, slow and induced labour. DESIGN: Prospective observational study. SETTING: The labour ward of a London teaching hospital. PARTICIPANTS: Forty patients were recruited from the antenatal clinic and labour ward of a West London Hospital. Five had normal onset and progression of labour, 14 had slow progression of labour and 21 had induced onset of labour. METHOD: Intrauterine pressure and head-to-cervix force was measured simultaneously using an intrauterine pressure catheter and a specially designed four sensor head-to-cervix force probe. RESULTS: For each contraction of each labour, scattergrams of force by pressure were plotted. Three patterns were observed. When the rise in pressure preceded the rise in force, a positive 'loop' was generated. When the rise in pressure and force occurred simultaneously a linear pattern was generated (a neutral 'loop'). When the rise in pressure lags the rise in force, a negative 'loop' was generated. In normally progressive labour the distribution of loops was 29.1%, 22.6% and 48.3%, respectively, in slow labour the distribution was 26.1%, 14.1% and 59.8% and in induced labour the distribution was 33.8%, 14.4% and 51.8%. These distributions were not statistically different. However, a higher proportion of negative loops was observed in labours augmented with oxytocin compared to those receiving no oxytocin (MW-U = 87, P = 0.036). No differences were observed comparing parity, use of PGE2, epidural analgesia, or mode of delivery. Contraction frequency (number/10 minutes) was inversely correlated to the percentage of negative loops (rs = -0.34, P = 0.033) and positively correlated with percentage of positive loops (rs = 0.36, P = 0.027). CONCLUSIONS: This is the first report of the temporal relation between intrauterine pressure and head-to-cervix force in labour. The most common pattern is that the rise in pressure lags the rise in force, suggesting that a seal has to be created between the fetal head and cervix before a rise in pressure can occur. When oxytocin is given in labour, a higher proportion of loops are negative indicating that there is poor application of the fetal head and cervix in a greater proportion of contractions.

Adult↗
PubMed1996

Head-to-cervix force: an important physiological variable in labour. 2. Peak active force, peak active pressure and mode of delivery.

OBJECTIVE: To assess the relation between peak active (above baseline) head-to-cervix force (paHCF) and peak active (above baseline) intrauterine pressure (paIUP) in labour, and to compare the relation between labours progressing well and ending in vaginal delivery and those labours progressing slowly and ending in caesarean section. DESIGN: Prospective observational study. SETTING: The labour ward of a London teaching hospital. PARTICIPANTS: Forty women in labour who agreed to have an experimental head-to-cervix force probe and an intrauterine pressure catheter inserted. RESULTS: The relation was linear, with a correlation coefficient which ranged from 0.012 to 0.885 (mean value 0.438). The closeness of the relation did not correlate with the rate of cervical dilatation (r = 0.0192, P = 0.574) or the mode of delivery (r = 0.215, P = 0.183). However, in women who progressed well to a vaginal delivery, the mean slope of the paHCF to paIUP regression line was 0.72, significantly steeper than in women who progressed slowly and required delivery by caesarean section (mean slope = 0.45, t = 2.31, P = 0.02). Mean paIUPs were significantly higher in women progressing well and achieving a vaginal delivery than in those progressing slowly and requiring caesarean section (45.3 mmHg SD 7.5 vs 38.4 mmHg SD 11.4, t = 2.31, P = 0.02), but the overlap between the two groups was considerable. However, in keeping with their steeper paHCF/paIUP slope, women progressing well to a vaginal delivery had substantially higher head-to-cervix forces (46.4 gWt SD 11.8 vs 28.3 gWt SD 8.2, t = 5.22, P < 0.00001) than those progressing slowly and requiring caesarean section, and there was much less overlap between paHCF than paIUP. This resulted in paHCF being a much better discriminating variable than paIUP for mode of delivery. CONCLUSIONS: The relation between paHCF and paIUP is linear, but there is a wide variation in the degree of correlation between one woman and another. Women with a steep slope of paHCF relative to paIUP are more likely to achieve a high mean paHCF, progress rapidly in labour and achieve a vaginal delivery than women with a flap slope, although mean paIUPs do not differ substantially between the two groups. The level of paHCF was substantially better than cervical dilatation rate at predicting mode of delivery. These results suggest that head-to-cervix force is sensitive to factors determining mode of delivery which are not reflected in either the level of uterine activity as measured by intrauterine pressure, or cervical compliance as measured by cervical dilatation rates.

Adult↗
PubMed2006

Impact of physiological variables and genetic background on myocardial frequency-resistivity relations in the intact beating murine heart.

Conductance measurements for generation of an instantaneous left ventricular (LV) volume signal in the mouse are limited, because the volume signal is a combination of blood and LV muscle, and only the blood signal is desired. We have developed a conductance system that operates at two simultaneous frequencies to identify and remove the myocardial contribution to the instantaneous volume signal. This system is based on the observation that myocardial resistivity varies with frequency, whereas blood resistivity does not. For calculation of LV blood volume with the dual-frequency conductance system in mice, in vivo murine myocardial resistivity was measured and combined with an analytic approach. The goals of the present study were to identify and minimize the sources of error in the measurement of myocardial resistivity to enhance the accuracy of the dual-frequency conductance system. We extended these findings to a gene-altered mouse model to determine the impact of measured myocardial resistivity on the calculation of LV pressure-volume relations. We examined the impact of temperature, timing of the measurement during the cardiac cycle, breeding strain, anisotropy, and intrameasurement and interanimal variability on the measurement of intact murine myocardial resistivity. Applying this knowledge to diabetic and nondiabetic 11- and 20- to 24-wk-old mice, we demonstrated differences in myocardial resistivity at low frequencies, enhancement of LV systolic function at 11 wk and LV dilation at 20-24 wk, and histological and electron-microscopic studies demonstrating greater glycogen deposition in the diabetic mice. This study demonstrated the accurate technique of measuring myocardial resistivity and its impact on the determination of LV pressure-volume relations in gene-altered mice.

Animals↗
PubMed1993

Effects of intracranial self-stimulation on selected physiological variables in rats.

The purpose of this investigation was to characterize selected metabolic, cardiovascular, and hormonal responses to reinforcing intracranial self-stimulation (ICSS) of the ventral tegmental area (VTA) in rats. Twenty male Sprague-Dawley rats were stereotaxically implanted with bipolar electrodes aimed at the VTA of the brain. Rats were trained to lever-press for ICSS for 1 wk. While they adapted to the experimental environment by sitting in a metabolic operant chamber, they were connected to the electrode cable but did not lever-press. All animals were instrumented with arterial catheters. Rats receiving contingent stimulation (C-St; n = 10) performed 30 min of lever pressing in the metabolic operant chamber for reinforcing brain stimulation. Oxygen consumption (VO2), heart rate (HR), mean arterial pressure (MAP), and rectal temperature (Trec) increased with the onset and continuation of contingent brain stimulation over 30 min (P < 0.05). In addition, plasma norepinephrine (NE), epinephrine (Epi), and corticosterone increased significantly above resting values in C-St rats (P < 0.05). Five animals received investigator-delivered reinforcing brain stimulation (noncontingent stimulation; NC-St), with MAP, HR, VO2, NE, and Epi increasing significantly above resting values (P < 0.05). Trec and corticosterone were not responsive to noncontingent brain stimulation. With the exception of HR, nonstimulated controls (n = 5) did not experience increases above resting values in any of the variables measured. The responses suggest that contingent brain stimulation reward elicits heightened sympathetic arousal.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗